U.S. patent application number 11/599266 was filed with the patent office on 2007-05-17 for vertical gan-based light emitting diode.
This patent application is currently assigned to SAMSUNG ELECTRO-MECHANICS CO., LTD.. Invention is credited to Tae Sung Jang, Pil Geun Kang, Tae Jun Kim, Su Yeol Lee.
Application Number | 20070108467 11/599266 |
Document ID | / |
Family ID | 37622864 |
Filed Date | 2007-05-17 |
United States Patent
Application |
20070108467 |
Kind Code |
A1 |
Jang; Tae Sung ; et
al. |
May 17, 2007 |
Vertical GaN-based light emitting diode
Abstract
A vertical GaN-based LED is provided. The vertical GaN-based LED
includes an n-type bonding pad, an n-type reflective electrode
formed under the n-type bonding pad, an n-type transparent
electrode formed under the n-type reflective electrode, an n-type
GaN layer formed under the n-type transparent electrode, an active
layer formed under the n-type GaN layer, a p-type GaN layer formed
under the active layer, a p-electrode formed under the p-type GaN
layer and having an uneven profile at a surface which does not come
in contact with the p-type GaN layer, a p-type reflective electrode
formed along the uneven surface of the p-type electrode, and a
support layer formed under the p-type reflective electrode.
Inventors: |
Jang; Tae Sung; (Suwon,
KR) ; Lee; Su Yeol; (Seongnam, KR) ; Kang; Pil
Geun; (Suwon, KR) ; Kim; Tae Jun; (Pyeongtaek,
KR) |
Correspondence
Address: |
MCDERMOTT WILL & EMERY LLP
600 13TH STREET, N.W.
WASHINGTON
DC
20005-3096
US
|
Assignee: |
SAMSUNG ELECTRO-MECHANICS CO.,
LTD.
|
Family ID: |
37622864 |
Appl. No.: |
11/599266 |
Filed: |
November 15, 2006 |
Current U.S.
Class: |
257/103 ;
257/E33.068; 257/E33.074 |
Current CPC
Class: |
H01L 33/22 20130101;
H01L 33/405 20130101 |
Class at
Publication: |
257/103 |
International
Class: |
H01L 33/00 20060101
H01L033/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 15, 2005 |
KR |
10-2005-0108872 |
Claims
1. A vertical gallium nitride (GaN)-based light emitting diode
(LED) comprising: an n-type bonding pad; an n-type reflective
electrode formed under the n-type bonding pad; an n-type
transparent electrode formed under the n-type reflective electrode;
an n-type GaN layer formed under the n-type transparent electrode;
an active layer formed under the n-type GaN layer; a p-type GaN
layer formed under the active layer; a p-electrode formed under the
p-type GaN layer, the p-electrode having an uneven profile at a
surface which does not come in contact with the p-type GaN layer; a
p-type reflective electrode formed along the uneven surface of the
p-type electrode; and a support layer formed under the p-type
reflective electrode.
2. The vertical GaN-based LED according to claim 1, wherein the
p-type electrode is formed of a transparent layer.
3. The vertical GaN-based LED according to claim 2, wherein the
transparent layer is formed of TCO or Ni/Au.
4. The vertical GaN-based LED according to claim 3, wherein the TCO
is a mixture made by adding at least one element selected from a
group consisting of Sn, Zn, Ag, Mg, Cu, and Al to indium oxide.
5. The vertical GaN-based LED according to claim 1, further
comprising an adhesive layer formed at an interface between the
p-type GaN layer and the p-electrode.
6. The vertical GaN-based LED according to claim 5, wherein the
adhesive layer is a transparent layer and is formed of a material
different from that of the p-electrode.
7. The vertical GaN-based LED according to claim 6, wherein the
adhesive layer is formed of a mixture made by adding at least one
element selected from a group consisting of Sn, Zn, Ag, Mg, Cu, and
Al to indium oxide, the element added to the adhesive layer being
different from the element added to the TCO forming the
p-electrode.
8. The vertical GaN-based LED according to claim 6, wherein the
adhesive layer is formed of a mixture made by adding at least one
element selected from a group consisting of Sn, Zn, Ag, Mg, Cu, and
Al to indium oxide, an amount of the element added to the adhesive
layer being different from an amount of the element added to the
TCO forming the p-electrode.
9. The vertical GaN-based LED according to claim 5, wherein the
adhesive layer has a thickness of 1-200 .ANG..
10. The vertical GaN-based LED according to claim 1, wherein the
support layer is formed using a plating seed by electroplating or
electroless plating.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of Korean Patent
Application No. 2005-108872 filed with the Korean Industrial
Property Office on Nov. 15, 2005, the disclosure of which is
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a vertical (vertical
electrode type) gallium nitride (GaN)-based light emitting diode
(LED) and a method of manufacturing the same. The vertical
GaN-based LED can increase the light extraction efficiency, thereby
improving the external quantum efficiency.
[0004] 2. Description of the Related Art
[0005] Generally, GaN-based LEDs are grown on a sapphire substrate.
The sapphire substrate is a rigid nonconductor and has a low
thermal conductivity. Therefore, it is difficult to reduce the size
of the GaN-based LED for cost-down or improve the optical power and
chip characteristics. Particularly, heat dissipation is very
important for the LEDs because a high current should be applied to
the GaN-based LEDs so as to increase the optical power of the
GaN-based LEDs. To solve these problems, a vertical GaN-based LED
has been proposed. In the vertical GaN-based LED, the sapphire
substrate is removed using a laser lift-off (hereinafter, referred
to as LLO) technology.
[0006] The vertical GaN-based LED according to the related art will
be described below with reference to FIG. 1.
[0007] Referring to FIG. 1, the conventional vertical GaN-based LED
includes an n-type bonding pad 110, an n-type reflective electrode
120, an n-type transparent electrode 130, an n-type GaN layer 140,
an active layer 150, a p-type GaN layer 160, a positive electrode
(p-electrode ) 170, and a support layer 190, which are sequentially
formed under the n-type bonding pad 110. The n-type transparent
electrode 130 is used for improving the current diffusion
efficiency.
[0008] In FIG. 1, a reference numeral 180 represents a plating seed
layer used as a plating crystal nucleus when the support layer 190
is formed by electroplating or electroless plating.
[0009] In the conventional vertical GaN-based LED, however, because
the p-electrode formed under the p-type GaN layer is formed of
Cr/Au, it absorbs or totally reflects some of light emitted from
the active layer. Thus, an entire luminous efficiency of the LED is
degraded.
SUMMARY OF THE INVENTION
[0010] An advantage of the present invention is that it provides a
vertical GaN-based LED in which a p-electrode is formed of a
transparent layer with an uneven surface so that the external
quantum efficiency is maximized and a current spreading effect is
improved so as to secure a high power characteristic.
[0011] Additional aspect and advantages of the present general
inventive concept will be set forth in the description which
follows and, in part, will be obvious from the description, or may
be learned by practice of the general inventive concept.
[0012] According to an aspect of the invention, a vertical
GaN-based LED includes: an n-type bonding pad; an n-type reflective
electrode formed under the n-type bonding pad; an n-type
transparent electrode formed under the n-type reflective electrode;
an n-type GaN layer formed under the n-type transparent electrode;
an active layer formed under the n-type GaN layer; a p-type GaN
layer formed under the active layer; a p-electrode formed under the
p-type GaN layer, the p-electrode having an uneven profile at a
surface which does not come in contact with the p-type GaN layer; a
p-type reflective electrode formed along the uneven surface of the
p-type electrode; and a support layer formed under the p-type
reflective electrode.
[0013] According to another aspect of the present invention, the
p-type electrode is formed of a transparent layer, more preferably,
TCO or Ni/Au. The TCO is a mixture made by adding at least one
element selected from the group consisting of Sn, Zn, Ag, Mg, Cu,
and Al to indium oxide.
[0014] According to a further aspect of the present invention, the
vertical GaN-based LED further includes an adhesive layer formed at
an interface between the p-type GaN layer and the p-electrode.
[0015] According to a still further aspect of the present
invention, the adhesive layer is a transparent layer and is formed
of a material different from that of the p-electrode.
[0016] According to a still further aspect of the present
invention, the adhesive layer is formed of a mixture made by adding
at least one element selected from a group consisting of Sn, Zn,
Ag, Mg, Cu, and Al to indium oxide, and the element added to the
adhesive layer is different from the element added to the TCO.
Moreover, it is preferable that an amount of the element added to
the adhesive layer is different from an amount of the element added
to the TCO forming the p-electrode.
[0017] According to a still further aspect of the present
invention, it is preferable that the adhesive layer has a thickness
of 1.about.200 .ANG. because its transmissivity decreases as its
thickness increases.
[0018] According to a still further aspect of the present
invention, the p-type reflective electrode has the uneven profile
at the surface that does not contact the support layer, and thus
the support layer is formed using a plating seed by electroplating
or electroless plating.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] These and/or other aspects and advantages of the present
general inventive concept will become apparent and more readily
appreciated from the following description of the embodiments,
taken in conjunction with the accompanying drawings of which:
[0020] FIG. 1 is a sectional view of a vertical GaN-based LED
according to the related art; and
[0021] FIG. 2 is a sectional view of a vertical GaN-based LED
according to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] Reference will now be made in detail to the embodiments of
the present general inventive concept, examples of which are
illustrated in the accompanying drawings, wherein like reference
numerals refer to like elements throughout. The embodiments are
described below in order to explain the present general inventive
concept by referring to the figures.
[0023] Hereinafter, a vertical GaN-based LED according to the
present invention will be described in detail with reference to
FIG. 2.
[0024] FIG. 2 is a sectional view of a vertical GaN-based LED
according to the present invention.
[0025] Referring to FIG. 2, an n-type bonding pad 110 for
electrical connection to an external device is formed at the
uppermost portion of the vertical GaN-based LED.
[0026] An n-type reflective electrode 120 for improving the
luminous efficiency is formed under the n-type bonding pad 110.
[0027] An n-type GaN layer 140 is formed under the n-type
reflective electrode 120. More specifically, the n-type GaN layer
140 may be formed of an n-doped GaN layer or an n-doped GaN/AlGaN
layer.
[0028] In order to improve the current spreading effect, an n-type
transparent electrode 130 is further formed at the interface
between the n-type reflective electrode 120 and the n-type GaN
layer 140.
[0029] An active layer 150 and a p-type GaN layer 160 are
sequentially formed under the n-type GaN layer 140, thereby forming
a GaN-based LED structure.
[0030] In the GaN-based LED structure, the active layer 150 may be
formed in a multi-quantum well structure with InGaN/GaN layer. Like
the n-type GaN layer 140, the p-type GaN layer 160 may be formed of
a p-doped GaN layer or a p-doped GaN/AlGaN layer.
[0031] A p-electrode 170 is formed under the p-type GaN layer 160
of the GaN-based LED structure. The p-electrode 170 is preferably
formed of a transparent layer, more preferably, transparent
conductive oxide (TCO) or Ni/Au. The TCO is a mixture made by
adding at least one element selected from the group consisting of
Sn, Zn, Ag, Mg, Cu, and Al to indium oxide.
[0032] Unlike the conventional p-electrode formed of Cr/Au, the
p-electrode 170 according to the present invention is formed of a
transparent layer such as TCO or Ni/Au. Therefore, an amount of
light emitted from the active layer and absorbed by the p-type
electrode is minimized, thereby improving both the luminous
efficiency and the current spreading effect.
[0033] Further, the bottom surface of the p-electrode 170, which
does not come in contact with the p-type GaN layer 160, has an
uneven profile. Therefore, the light emitted from the active layer
is scattered by the uneven surface, thereby maximizing the external
quantum efficiency.
[0034] Although not shown, an adhesive layer may be further formed
at an interface between the p-electrode 170 and the p-type GaN
layer 160 so as to increase their adhesive strength. As the
thickness of the adhesive layer increases, its transmittance
decreases. Therefore, it is preferable that the adhesive layer has
a thickness of 1.about.200 .ANG..
[0035] The adhesive layer is formed of a transparent layer.
However, it is preferable that the adhesive layer is formed of a
material different from that of the p-electrode 170. More
specifically, in order to obtain the excellent adhesive strength,
the adhesive layer is formed of a mixture made by adding at least
one element selected from the group consisting of Sn, Zn, Ag, Mg,
Cu, and Al to indium oxide. It is preferable that the element added
to the adhesive layer is different from the element added to the
TCO, or an amount of the element added to the adhesive layer is
different from an amount of the element added to the TCO.
[0036] A p-type reflective electrode 200 is formed along the uneven
surface of the p-electrode 170. Therefore, the p-type reflective
electrode 200 also has the uneven profile, so that the light
emitted from the active layer 150 can be prevented from being
totally reflected and lost.
[0037] Under the p-type reflective electrode 200, a support layer
190 is formed of a plating layer. The plating slayer is formed
using a plating seed layer 180 by electroplating or electroless
plating.
[0038] Although the support layer 190 is provided with the plating
layer formed by using the plating seed layer 180 as a crystal
nucleus, the present embodiment is not limited thereto. That is,
the support layer may be formed of a Si substrate, a GaAs
substrate, a Ge substrate, or a metal layer, which can serve as a
support layer of a final LED and an electrode.
[0039] In addition, the metal layer may be formed using thermal
evaporator, e-beam evaporator, sputter, and chemical vapor
deposition (CVD).
[0040] As described above, the p-electrode is formed to have the
uneven surface, so that the light emitted from the active layer can
be prevented from being absorbed or scattered by the p-electrode.
Then, it is possible to improve the light extraction efficiency and
maximizing the external quantum efficiency.
[0041] Furthermore, the current spreading effect is improved by
forming the p-electrode of the transparent layer, thereby obtaining
the high power characteristic.
[0042] Consequently, the present invention can improve the
characteristics and reliability of the vertical GaN-based LED.
[0043] Although a few embodiments of the present general inventive
concept have been shown and described, it will be appreciated by
those skilled in the art that changes may be made in these
embodiments without departing from the principles and spirit of the
general inventive concept, the scope of which is defined in the
appended claims and their equivalents.
* * * * *